High-temperature development of photographic materials



7 No Drawing.

rarss PATENT OFFICE.

ALEXANDER JOHNSTON AGNEW AND FRANK FORSTER RENWIGK, OF ILIORD, ENGLAND, ASSIGNORS TO ILFORD LIMITED, 0F ILFORD, ENGLAND.

HIGH-TEMPERATURE DEVELOPMENT OF PHOTOGRAPHIC MATERIALS.

T 0 all whom it may concern Be it known that we, ALEXANDER JOHN- STON AGNEW and FRANK FoRs'rnR RnNwIoK, subjects of the King of England, and both residing at Ilford, in the county of Essex, England, have invented certain new and useful Improvements in High-Temperature Development of Photographic Materials, of which the following is a specification.

This invention is for improvements in or relating to high-temperature development or other treatment by aqueous solutions of photographic, materials, and has forits object to provide a process whereby these materials may be safely manipulated in tropical countries, or in abnormally hot weather elsewhere.

Special developers have heretofore been proposed for developing in these circumstances, but such developers have usually a strong tendency to fog, the development is so rapid that it cannot be conveniently controlled, and they are of little use at a temperature of 90 F. or over.

According to the present invention, a

hardening bath or mixture is provided for treating gelatine-surfaced photographic materials prior to subjecting them to the action of a developer or other aqueous solution, which bath contains formaldehyde solution, paraform, or a compound from which formaldehyde is readily obtained, together with a salt (for example, sodium citrate or sodium sulphate or di-sodium ortho-phosphate) of the known class which tends to raise the melting point of a gelatine V jelly and to retard or restrict the swelling of dry gelatine in water.

The invention further consists in the process for developing or otherwise treat.- ing by aqueous solutions gelatine-surfaced photographic materials at high temperatures consisting in first subjecting the material to a hardening bath such as above described, and then subjecting it to a developer or other aqueous solution, It is found that if a photographic plate, for example, be first hardened in the aforesaid manner, it can afterwardsbe developed or say toned with ease by any of the known developers or toning baths at a high temperature.

Specification of Letters Patent.

Patented July 25, 19122.

Application filed February 28, 1919. Serial No. 279,882.

The class of salts referred to includes acetates, tartrates', citrates, oxalates, sulphates, phosphates, chromates, bicarbonates, and borates.

A formula for this preliminary bath may be as follows 40% formaldehyde solution 10 c.c.m. Sodium sulphate crystals 80 grams. Or di-sodium orthophosphate- 40 grams. Water up to 400 0.0..

or if paraform be employed 4.5 grams of this may be used instead of the 10 c. c. of formaldehyde solution.

The above formula may be compounded and kept indefinitely, or the paraform and sodium sulphate or other salt in anhydrous form may be made up as powders or into pellets and sold in this condition for dissolving when required in the necessary quantity of water.

It will be appreciated that the formula for the purpose of this invention may be variously modified without departing from the spirit of the invention, various salts other than sodium sulphate being available as already described. Almost any base may be employed that will give a soluble salt though allare not equally good but besides sodium salts ammonium and magnesium have been found to give good results.

It has been found that by using this preliminary bath, photographic plates and other materials can be manipulated that is developed, toned, fixed, washed or otherwise treated with aqueous solutions at a temperature as high as 110 F. without any cooling means being necessary. The salt retards the swelling and prevents melting of the gelatine while the formaldehyde solution is penetrating and combining with it to form this hardening, enables the developing to be carried out afterwards without undue haste, Whereas when the hardening material has been incorporated in the developer, the hardening action has scarcely begun before development is finished and this is so rapid that, as already stated, it cannot be controlled; moreover, the hardening effect being imperfect, subsequent treatment, such as fixing and washing of the plate is exceedingly difficult and at such temperatures as 100 to 110 F. it is impossible even to complete development itself before the gelatine melts. lVhen, however, the hardening is effected in a preliminary bath as described, the developing and fixing and Washing can'all be subsequently carried out in practically the same manner and with almost as much ease as would be the case if operating in ordinary, temperatures.

The advantages referred to above as the result of applying this invention to developing also accrue in part to other manipulations such as toning.

It will be understood that the invention is applicable to all gelatine-surfaced photographic materials, such for example as plates, papers, and films.

In practice it is usual to proceed with development immediately after rinsing off the excess of the preliminary hardening bath.

What we claim as our invention and desire to secure by Letters Patent is 1. A composition for treating gelatinesurfaced photographic materials for harden ing them only, comprising a substance adapted to yield formaldehyde together with a relatively greater amount of a salt of the known class which tends to raise the melting point of a gelatine jelly and to retard or restrict. the swelling of gelatine in water.

2. A composition for treating gelatine surfaced photographic materials for harden ing them only, comprising a substance adapted to yield formaldehyde together with a salt of theknown class which tends to raise the melting point of a gelatine jelly and to retard or restrict the swelling of gelatine in water, in concentration in excess of one molecular proportion relatively tothe formaldehyde yielding substance to preserve the consistency of the gelatine surface pending reaction therewith of the formaldehyde.

3. A composition for treating gelatinesurfaced photographic materials for hardening them only, comprising a substance adapted to yield formaldehyde together with an alkali salt of the known class which tends to raise the melting point of a gelatine jelly and to retard or restrict the swelling of gelatine in water, in concentration in excess of one molecular proportion relatively to the formaldehyde yielding substance to preserve the consistency of the gelatine surface pending reaction therewith of the formaldehyde.

4:. A composition for treating gelatinesurfaced photographic materials for hardening them only, comprising a substance adapted to yield formaldehyde together with a sodium salt of the known class which tends to raise the melting point of a gelatine jelly and to retard or restrict the swelling of gelatine in water, in concentration in excess of one molecular proportion relatively to the formaldehyde yielding substance to preserve the consistency of the gelatine surface I pendingreaction therewith of the formal-v dehyd a 5. A composition for treating gelatine-V ing point of a gelatine jelly and to retard or restrict the swelling of gelatine in water in such concentration as to preservethe consistency of the gelatine surface pending reaction therewith of the formaldehyde.

7 A composition for treating gelatinesurfaced photographic materials for hardening themonly, comprising a solution of free formaldehyde together with an alkali salt of the known class which tends to raise the melting point of a gelatine jelly and to retard or restrict the swelling of gelatine in water in such concentration as to preserve the consistency of the gelatine surface pending reaction therewith of the formaldehyde.

8. A composition for treating gelatinesurfaced photographic materials for hardening them only, comprising a solution of free of the known class which tends to raise the melting point of a gelatine jelly and to retard or restrict the swelling of gelatine in water, in such concentration as to preserve the consistency of the gelatine surface pending reaction therewith of the formaldehyde.

9. A composition for treating gelatinesurfaced photographic materials for harden- 1ng them only, comprising a solution of free formaldehyde together with sodium citrate in such concentration as to preserve the consistency of the gelatine surface pending reaction therewith of the formaldehyde.

10. A process for hardening gelatinesurfaced photographic materials comprising sub ecting the material to treatment in a bath comprising formaldehyde together with 3110 formaldehyde together with a sodium salt In testlmony whereof We have signed bar names to this specific-( tion in the presence of two subscribing Witnesses.

ALEXANDER JOHNSTON AGNEW. FRANK FORSTER RENWICK.

Witnesses:

A. M. HARWARD, HARRY S. LINDGE. 

